Rail car brake apparatus

ABSTRACT

A parallel beam brake apparatus for dual and triple axle trucks and a single beam brake apparatus for single axle trucks each comprise spaced, pivotably mounted bell crank levers which engage a fluid operable actuator between one pair of arms and engage a pair of push rods with the remaining arms. Improved spherical joints between the arms and the push rods facilitate force tranmsmission without allowing push rod rotation. A unique pivot geometry between the bell crank levers and the brake beams facilitates assembly and improves stress distribution between the levers and the beams. The actuator includes a slack adjustor mechanism in which a spiral power spring unwinds to drive a lead screw and take up slack or is wound by the rotating, translating lead screw to add slack.

This application is a division, of application Ser. No. 776,762 filed onSept. 16, 1985, abandoned.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates in general to brake apparatus for use onrail cars. More particularly, the invention concerns an improved type ofsingle cylinder, truck mounted brake apparatus, the cylinder comprisinga slack adjuster.

Such single cylinder truck mounted brake apparatus have been in use forsome time. For example, U.S. Pat. Nos. 3,780,837, to Haydu, and4,060,152, to Bogenschutz et al, disclose rail car brake apparatus ofthis general type.

While such prior art brake apparatus have achieved a measure of success,various problems and drawbacks have been noted. In most cases, the priorart brake apparatus have been designed for use on either single axle ordual axle or triple axle trucks; so that, a given prior art brakeapparatus typically cannot be readily removed from a rail car with onetype of truck and installed on another with a different type of truck,without rather extensive modification.

Prior art apparatus of the type disclosed in the Haydu patent have alsobeen criticized because of the rather large amount of pressurized fluidrequired to stroke their long-stroke actuators, especially thoseactuators having no provision for slack adjustment. Provision of longstroke capability is desirable to permit the use of thicker, longerlasting brake shoes. Where slack adjustment is provided, the prior artactuators frequently adjust only for increases in brake shoe clearancedue to wear, but not for decreases in brake shoe clearance due to shoeor wheel replacement. Also, prior art slack adjusters do not begin tooperate until the brake shoe engages the wheel. This delays theadjustment and possible uneveness in the brake application. Someadjusters require a number of brake application cycles before they areproperly adjusted.

Another drawback of many prior art apparatus of this type has concernedthe manual parking brake mechanism. Frequently, as in the older parallelbeam systems, the parking brakes are applied by means of a linkagemounted on one side of the truck, to provide clearance with the centralportions of the truck and bolster. Due to the off-center mounting of theparking brake linkage, the brakes tend to be applied first on the sidenearer the linkage mount and then, if at all, on the side further fromthe linkage mount. Due to the point of force application, high stressesare induced in the beams, which must be of heavy construction. Theoff-center mounting also may result in application of insufficientbraking force in cases where contact is made only on one side.Furthermore, crewmen checking a car to ensure parking brake applicationmay mistakenly conclude that the brake has not been applied afterlooking at the shoes and wheels on the side opposite the linkage mount.In addition to the off-center mounting to clear the truck and bolster,large openings had to be cut in the bolster to allow assembly of thebrake system and clearance for the cylinder and connecting rods. Oneprior art solution to these type of problems is disclosed by Bogenschutzet al.

Still another difficulty with such prior art apparatus has concerned theamount of disassembly required to remove and repair various elements ofthe apparatus. For example, it is sometimes not possible or is quitedifficult to remove the actuator without disassembling a good portion ofthe rest of the brake apparatus.

A primary object of the present invention is to provide an improvedbrake apparatus or rigging for rail vehicles, the rigging being readilyadaptable for use on vehicles having single, dual or triple axle trucks.

Another object of the invention is to provide an improved truck mountedbrake apparatus having a fluid pressure actuated brake cylinder with adouble-acting mechanical slack adjuster which automatically adjusts theclearance between the brake shoe and wheel to provide a constantclearance prior to each brake application, irrespective of brake shoe orwheel wear or replacement of shoes or wheels.

Still another object of the invention is to provide rapid take-up of theclearance after brake shoes have been replaced.

A further object of the invention is to provide a brake cylinder forsuch a brake apparatus, the cylinder being mounted to one of the brakebeams and including means for manually stroking the actuator to applyparking brakes just as during normal application; whereby, uniformparking brake application is achieved at all wheels on both sides of therail car truck.

Even another object of the invention is to provide a slack adjusterwhich permits "barring back" of the brake shoe manually to increase theshoe clearance.

Yet another object of the invention is to provide a parking brakeoperable by cables from a remote location to provide uniform parkingbrake application at all wheels.

Still another object of the invention is to provide a parallel beambrake apparatus having light weight channel-type brake beams andimproved actuating and connecting linkages which minimize bendingmoments in the beams.

A still further object of the invention is to provide such a brakeapparatus in which the light weight brake beams are attached toreplaceable brake heads and in which improved spherical joints are usedfor connecting push rods to actuator bell crank levers.

An even further object of the invention is to provide a brake apparatuswhich optimizes the actuation angle of travel without modifying thetruck bolster.

The above objects of the invention are intended to be only exemplary;so, other desirable objectives and advantages inherently achieved by thedisclosed invention may occur or become apparent to those skilled in theart. Nonetheless, the scope of the invention is to be limited only bythe appended claims.

The brake apparatus according to the invention is particularly adaptedfor use in rail vehicles having one, two or three transverse axles ateach truck. At least one brake beam is mounted to each truck of thevehicle and extends in spaced, parallel relation to the axle formovement longitudinally of the vehicle. The brake beam includes at itsopposite ends a pair of brake shoe carrying heads and each of the brakeshoe carrying heads comprises a pivot means. A pair of bell crank leversis provided, each lever having a fulcrum and a pair of arms. One bellcrank lever is mounted to each brake shoe carrying head with the fulcrumof the bell crank lever supported by the pivot means of the brake shoecarrying head. A fluid pressure operable brake cylinder is pivotablymounted at one end to one arm of one of the bell crank levers and at theother end to one arm of the other bell crank lever.

In such a brake rigging, one improvement of the invention comprises apair of push rods each comprising at one end a clevis having a firstaxis of rotation, the clevis having arms with first bores spaced alongthis first axis. A spherical bearing member is positioned between thearms, the bearing member having a concave spherical bearing surface witha center of curvature positioned on the first axis. Means, such as aretaining pocket between the arms, are provided for holding the bearingmember. The other arm of each of the bell crank levers has at its end aconvex spherical bearing surface and a second bore having a second axisextending through the center of curvature of the convex sphericalbearing surface. Means such as a pin or bolt extend through the firstand second bores to pivotably couple the push rods to the bell cranklevers with the spherical bearing surfaces in contact.

In accordance with another improvement of the invention, the pivot meansformed in the brake shoe carrying heads comprises axially spaced boreshaving spaced, axially aligned and radially outwardly opening accessslots. A transversely extending, outwardly opening space is definedbetween the axially spaced bores. The fulcrums formed in the bell cranklevers include axially extending bosses or gudgeons sized to passradially through the access slots so that the bell crank levers extendinto the outwardly opening spaces and the bosses or gudgeons arepositioned in the axially spaced bores. The bosses are provided with acommon central bore. Bearing members rotatably support the bosses withinthe axially spaced bores and means such as a pin or bolt extend throughthe bearing members and the central bore to pivotably couple the bellcrank levers to the brake shoe carrying heads. This allows positioningthe pivot closer to the longitudinal center of the truck.

To provide additional support for the bell crank levers, the brake shoecarrying heads preferably comprise upwardly facing wear surfacesadjacent the lowermost of the axially spaced bores and the bell cranklevers slide along these wear surfaces during brake applications andrelease. The other end of each push rod may be fixed to a parallel,secondary brake beam mounted adjacent a second axle in a dual or tripleaxle truck, or may be pivotably attached to a pull rod fixed to the sametransverse axle.

The fluid pressure operable brake cylinder or actuator according to theinvention comprises a housing having an interior bore within which apiston is mounted for reciprocating movement in response topressurization and depressurization of a volume defined between thepiston and the housing. A spring is positioned between the piston andthe housing for biasing the piston toward a brakes-released position. Alead screw is rotatably and translatably supported at one end by thepiston. Clutch means are operatively connected between the lead screwand the piston for selectively allowing or preventing rotation of thelead screw relative to to the piston. Means actuated by movement of thepiston in the bore are provided for engaging the clutch means when thepiston is in the brakes-released position and for releasing the clutchmeans as the piston moves between the brakes-released position and abrakes-applied position. The clutch means is also engaged in thebrakes-applied position. A torsion power spring is operatively connectedbetween the piston and the lead screw for rotating the lead screw orbeing wound by rotation of the lead screw when the clutch means isreleased; whereby, the lead screw is extended by the torsion springmeans to take up slack, or retracted to wind the torsion spring meansand provide slack, in an associated brake apparatus.

The clutch means preferably comprises a first pair of axially spacedclutch faces operatively connected to the piston, a clutch head mountedfor rotation and axial translation within the piston, the lead screwbeing connected to the clutch head for rotation and translationtherewith, and a second pair of axially spaced clutch faces operativelyconnected to the clutch head, the second pair being positioned betweenand juxtaposed to the first pair. The means for engaging, releasing andengaging the clutch means comprises a clutch operating lever pivoted tothe piston, a clutch spring operatively associated with the clutch head,and a plunger slidably mounted in the piston in position to be pushed bythe clutch operating lever when the lever contacts the housing. Movementof the plunger compresses the clutch spring and thereby releases one setof clutch faces from the brakes-applied position. Continued compressionof the clutch spring subsequently engages the other set of clutch facesin the brakes-released position.

The lead screw is threaded through a nut, the nut being attached to apush rod slidably mounted in the housing for movement between thebrakes-released and brakes-applied positions. As a result, force appliedto the push rod in the brakes-released position causes the other set ofclutch faces to disengage and thereby allows the lead screw to rotatethrough the nut and wind the torsion spring means.

In accordance with a further improvement of the invention, the actuatorcomprises a pair of telescope tubes attached to its piston and extendingaway from the volume defined between the piston and its housing. Thesetubes extend parallel to the lead screw of the actuator and a pair ofhand brake actuator cables slidably extend into the housing and intorespective ones of the telescope tubes. Means are operatively associatedwith the cables and the tubes for allowing the tubes to telescope overthe cables when the piston moves in response to fluid pressure but forallowing the cables to move the piston toward the brakes-appliedposition in response to tension applied to the cables.

Other objects, advantages and novel features of tne present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partially fragmentary view of a parallel beamrail car brake apparatus embodying the improvements of the presentinvention, indicating the orientation of the various elements of theinvention relative to the axle and wheels of such a rail car.

FIG. 2 is a perspective, partially fragmentary view of a single beamrail car brake apparatus for use on single axle trucks.

FIG. 3 shows a fragmentary, perspective view of a brake shoe carryinghead and bell crank lever according to the invention, indicating themode of pivotable connection between the trake shoe carrying head andthe bell crank lever.

FIG. 4 shows a perspective, fragmentary view of the spherical bearingjoint between one arm of the bell crank lever and the push rod of thebrake apparatus.

FIG. 5 shows a perspective, partially fragmentary view of the pivotablejoint between a push rod and brake shoe carrying shoe carrying head ofthe secondary brake beam shown in FIG. 1.

FIG. 6 shows an elevation, partially sectioned and fragmentary view ofthe pivotable joint between the bell crank levers and the fluid operableactuator according to the invention.

FIG. 7 shows an elevation view, partially in section, of a fluidoperable actuator according to the invention, indicating the relativeposition of the components of the device in the brakes-releasedposition.

FIG. 8 shows the actuator of FIG. 7 when the piston has moved to theleft in response to fluid pressure, just prior to release of the clutchto allow rotation of the lead screw by the torsion spring.

FIG. 9 shows a view of the apparatus of FIGS. 7 and 8 when the actuatorhas been extended to the brakes-applied position.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to FIGS. 1 and 2, the overall geometry and operation ofthe brake apparatus according to the invention may be understood. FIG. 1shows the arrangement used on a double axle truck and FIG. 2 shows thearrangement used on a single axle truck. A conventional rail car wheeland axle assembly 10 is illustrated fragmentarily. Located between andparallel with rail and axle assembly 10 and a similar assembly on theopposite side of the truck, not illustrated, are a primary or masterbeam 12 and a secondary beam 14. Beams 12 and 14 are movably mounted inconventional side frame members of the associated truck, notillustrated. Primary beam 12 comprises a central, rolled steel channelportion 16 having a pair of cast brake shoe carrying heads 18 hulkbolted thereto at either end. Brake heads 18 include integral, outwardlyprojecting guide feet 20 which are slidably received in slots located inthe side frame members of the associated truck in the usual manner, aswill be appreciated by those skilled in the art. Secondary beam 14comprises a central, rolled steel channel portion 22 to which areattached cast brake shoe carrying heads 24 which are hulk bolted theretoat either end. Brake shoe carrying heads 24 also include outwardlyprojecting guide feet 26 which are likewise slidably received in theside frame members of the associated truck. Finally, conventionalcomposition brake shoes 28 are attached to the brake shoe carrying heads18, 24.

A pair of forged steel bell crank levers 30 are pivotably mounted tobrake heads 18 of the primary beam 12. Each bell crank lever 30 includesa braking force receiving arm 32 which extends outwardly and upwardly onone side of the primary beam and a braking force transferring arm 34which extends outwardly and downwardly on the other side of the primarybeam. Between arms 32 and 34, each bell crank lever 30 comprises a pivot36 about which the arms rotate when pivot 36 is mounted to theassociated brake shoe carrying heads in the manner shown in FIG. 3. Arms34 are sized to be as short as practical so that pivot 36 may be locatedas close as possible to the outboard ends of the master beam 12. Thislocation of the pivots 36 ensures that the optimum force will betransferred from the actuator to the brake heads on both means while aminimum amount of bending stress will be generated in primary beam 12.The closer pivot points 36 are to the middle of primary beam 12, thegreater are the bending stresses in use and the heavier must be thecross section of central channel portion 16.

A pneumatically operable brake cylinder 38, including a double actingslack adjuster 40, is pivotably connected to arms 32 at pivots 42 and44. Additional details of brake cylinder 38 and slack adjuster 40 willbe discussed with regard to FIGS. 7-9. A pair of armored cables 46 and48 are provided for manually actuating brake cylinder 38. The ends ofthe sheaths of cables 46, 48 remote from actuator 38 are fixed tobracket 50 attached to the underside of the associated bolster or anyother convenient location on the undercarriage of the car. The ends ofthe enclosed cables are pivotably attached to an evener bar 52 which inturn is linked to the lower end of an actuator lever 54 pivotablymounted to the car in the familiar manner. At the upper end of actuatorlever 54, a chain 56 is attached which extends to a conventional handbrake actuator, not illustrated.

A pair of push rods 58 are pivotably connected to arm 34 at sphericalpivot joints 60, discussed in greater detail with respect to FIG. 4. Theopposite ends of push rods 58 are joined to secondary beam 14 at pivotjoints 62, illustrated in FIG. 5. Pivot joints 62 are located so thatwhen the brakes are actuated, push rods 58 will assume a positionvirtually perpendicular to both primary beam 12 and secondary beam 14 toensure transmission of optimum braking force to the rail car wheels.That is, spherical joint 60 is located slightly outboard of pivot joint62 when the brakes are in their released position. Thus, as bell cranklevers 30 rotate, push rods 58 tend to move to a position perpendicularto both brake beams.

During operation, pneumatic pressure is applied to brake cylinder 38,causing pivots 42 and 44 to move apart, rotating bell crank levers 30about pivots 36. As the bell crank levers rotate, brake heads 28 mountedon secondary beam 14 will first move into contact with the adjacentwheels, due to force transmitted by push rods 58. After contact isestablished at these wheels, continued expansion of brake cylinder 38will cause bell crank levers 30 to pivot about spherical joints 60 andthus move brake heads 28 of primary beam 12 into contact with theadjacent wheels 10. Thus, the braking force is applied equally at allwheels at both ends of each braking beam. During manual application ofthe brakes, brake cylinder 38 functions identically so that equalbraking force is applied at all wheels during manual brake applicationas well.

The geometry of the brake rigging shown in FIG. 1 permits significantsimplification of the brake beams. Because the push rods 58 joinsecondary beam 14 at pivot joints 62 located just inboard of brake heads28, relatively low bending stresses are induced during operation. Also,axial loading of the bolted joint is minimized. As a result, centralchannel portion 22 may be relatively small in cross section. Inaddition, the design flexibility of a geometrically complex brake headis retained due to the use of cast brake shoe carrying heads, while thefinal beam assembly is simplified due to the use of simple boltedjoints. Primary beam 12 is also simplified compared to prior art castbeams; however, the location of pivot points 36 on tne primary beamrequires the use of a larger central channel portion 16. By making arms34 as short as possible, consistent with a required movement of thebrake heads 28 and the stroke capabilities of the actuator 38, thebending stress in the primary beam also may be minimized.

As will be explained more fully below with respect to FIG. 3, thestructure of bell crank lever 30 and its mounting to primary beam 12allows the pivot 36 to be closer to the longitudinal center of the truckand further away from the wheel 10. Bell crank lever 30 is configured totake advantage of this increased distance for greater pivotal motion.The bell crank arm 30 rotates from an oblique angle from thelongitudinal axis, through 90° to an acute angle.

FIG. 2 shows a modification of the apparatus of FIG. 1 which isespecially adapted for use with single axle trucks. In this case, theguide feet 20 are modified to accept a ball and socket joints 64attached to lower ends of suspension links 21 pivotably attached to theundercarriage of the car in a manner not specifically illustrated. Thepush rods 58 extend in the opposite direction to that of FIG. 1 and areattached by means of a pivot joint 62 to a cast bearing adapter 66mounted on the end of the axle assembly. Adapter 66 comprises integralmounting lugs 68 for attachment to pivot joint 62. In this embodiment,application of force to bell crank levers 30 causes the levers to pivotabout spherical joints 60 so that the brake shoes are brought intocontact with the associated wheels. Taking the reaction force of thebeam in this way allows cancellation of the high brake shoe normalforces acting on the axle. Thus, braking causes no net longitudinalforce at the axle and does not interfere with the ability of the axle toyaw or with curving of a single axle vehicle.

FIG. 3 shows a perspective, exploded view of the pivot joint betweenbrake shoe carrying head 18 and bell crank lever 30. The brake shoecarrying head comprises, on its side facing away from the wheelassembly, an upwardly opening recess 70 which terminates at its lowerend at a wall segment 72. On the underside of the brake shoe carryinghead 18 a depending support flange 74 is provided. A pair of axiallyseparated and aligned bores 76, 78 are provided through wall segment 72and support flange 74. A pair of axially separated, aligned and radiallyoutwardly opening access slots 80, 82 open from the exterior of thebrake shoe carrying head into bores 76, 78 to define key holes. Eachbell crank lever 30 comprises a pair of axially extending cylindricalbosses or gudgeons 84, 86 which are sized to be insertable into bores76, 78 through access slots 80, 82. A central bore 88 extends throughbosses 84, 86. When the bosses are inserted into bores 76, 78, the bodyof bell crank lever 30 is positioned within a space 90 defined betweenwall segment 72 and support flange 74. A pair of cylindrical brassbearing members 92, 94 fit between bosses 84, 86 and bores 76, 78 andare retained in position by radially extending support flanges 96, 98.The assembly of pivot 36 is completed by a fastener such as a bolt 100and nut 102 which bear upon the outer surfaces of bearing members 92,94. Due to the presence of bearing members 92, 94, the load on pivot 36is not taken by bolt 100 but is transmitted directly to the bearingmembers and the body of the beam. Thus, the use of key hole bores ispermissible since no force toward access slots 80, 82 is produced. Thisarrangement of the components of pivot 36 facilitates initial assemblyof the primary beam and also facilitates removal of a bell crank leverfrom an installed brake rigging, if necessary.

FIG. 4 shows an exploded perspective view of spherical pivot joints 60.Each joint 60 comprises a clevis 124 attached to one end of push rod 58,the clevis having a pair of axially spaced arms 126, 128 through whichcentral bores 130 extend to define an axis of rotation. A concavespherical bearing insert 132 is provided which has its center ofcurvature located on the axis of central bore 130. To retain bearingmember 132, a retaining pocket 134 is provided between arms 126, 128. Onthe mating end of arm 34 of the associated bell crank lever 30, a convexspherical bearing surface 136 is provided surrounding a central bore 138whose axis coincides with the center of curvature of bearing surface136. A pair of brass bearing members 140, 142 having radially extendingretention flanges 144, 146 are fitted within central bore 138. Whenconvex bearing surface 136 is placed in engagement with concave bearingsurface 132, a bolt 148 is passed through central bore 130 and bearingmembers 140, 142 and is secured by means of a nut 150 to complete thejoint. The fastening of the clevis 124 through the center of curvatureof the spherical joint, as shown in FIG. 4, serves to prevent the pushrod 58 from rotating, thus assuring that the length adjustment of thepush rod 58 at the secondary beam cannot change once the push rod hasbeen installed.

FIG. 5 shows a perspective, exploded view of a pivot joint 62 at thesecondary beam in FIG. 1 or between the push rod and the bearing adapter66 in the embodiment of FIG. 2. Push rod 58 comprises a threaded end 104which is threaded into a rod end sleeve 106 having an associated locknut thereby permitting adjustment of the effective length of push rod58. Attached to the end of sleeve 106 is an annular bushing support 108within which is bonded a rubber vibration damping bushing 110 having acentral metal sleeve 112 with a central bore 114. The brake shoecarrying head 24 of the secondary beams is provided with a dependingflange 116 so that a rod end pocket 118 is defined. In FIG. 2, thepocket is defined between lugs 68. A through bore 120 in the body ofbrake shoe carrying head 24 and a further through bore 122 in dependingflange 116 are sized to pass a suitable pin or bolt, not illustrated,which secures pivot joint 62. A similar arrangement is used betweenjoint 62 and clevis 68 in the embodiment of FIG. 2.

FIG. 6 shows a fragmentary elevation view through pivot joints 42, 44.As shown in the Figure, brake force receiving arm 32 comprises anupwardly angled portion 152 which permits the brake actuator 38 to bepositioned at a relatively higher location behind the bolster than wasachievable with the brake apparatus disclosed by Bogenschutz et al. Arm32 terminates in an essentialy horizontally extending boss 154 whichfits between a pair of attachment lugs 156, 158 provided at either endof the actuator 38, as shown in FIGS. 7-9. A vibration damping washer160 is positioned between boss 154 and lugs 156, 158. Preferably, washer160 comprises a pair of metal washers 162, 164 between which is bonded arubber washer 166. Means such as a pin 170 extend through washer 160 andbores provided through lugs 156, 158. A retainer such as a cotter key172 may be used to retain pin 170. An upwardly facing wear surface 173is provided on the upper surface of flange 74, to support bell cranklever 30 as it rotates.

FIG. 7 shows an elevation view, partially in section, of a brakeactuator 38 having a slack adjuster 40 in accordance with the presentinvention. The actuator is shown in the brakes-released position. Ahollow cylinder bottom 174 is attached by suitable means such bolts, notillustrated, to a hollow cylinder top 176. An actuator guide tube 178extends into cylinder top 176 via a bore 180 in the end wall of cylindertop 176. Guide tube 178 may be welded to cylinder tube 176 or otherwiseattached. Slidably mounted within actuator guide tube 178 is atelescoping hollow push rod 182 which comprises a threaded insert 184press fitted into its internal diameter at its inner end. A bearingsleeve 186 is welded to the exterior surface of push rod 182 at itsinner end and slidably engages the inner diameter of guide tube 178. Atits outer end, push rod 182 is welded to an end fitting 188 whichcomprises attachment lugs 156, 158 previously referred to. A similarpair of lugs are provided on the outer end of cylinder bottom 174. Atthe outer end of guide tube 178, a threaded retaining nut 190 isprovided which houses on its inside diameter a wiper seal 192 engagingpush rod 182. A further bearing member 193 is captured between retainingnut 190 and the end of actuator guide tube 178 to provide additionalsupport for push rod 182 during operation. A lead screw 194 ispositioned within push rod 182 and extends through threaded insert 184in position to engage a piston assembly 196.

The piston assembly 196 is mounted for translation within the housingmade of cylinder bottom 174 and cylinder top 176 and comprises a piston198 which slides within a cylinder 200. A seal 202, such as a T-seal,and a wear ring 204 extend between piston 198 and cylinder 200 in thefamiliar manner. An inlet 206 for pressurized fluid such as air extendsthrough the wall of cylinder bottom 174 into an interior volume 208defined between piston 198 and cylinder bottom 174.

On the side of piston 198 facing into volume 208, a rightwardly opening,as illustrated, counter bore 210 is provided which has a radiallyinwardly extending annular bottom ledge 212 on which an annular clutchface insert 214 is seated. A further bore 216 opens from the innerdiameter of bottom ledge 212 and extends leftwardly into a leftwardlyopening counter bore 218 formed in piston 196 and extended leftwardly toan annular end surface 220 of piston 198. Counter bore 218 is closed, inpart, by an annular piston head plate 222 having a central bore 224. Aretaining ring 226 holds head plate 222 within counter bore 218.

Mounted within counter bores 210, 216 and 218 is an elongated,cylindrical clutch head assembly 228 which both rotates and translateswithin these bores. Assembly 228 is supported by means of a pair ofbearings 230,232 which are attached to the outer surface of headassembly 228 by suitable retaining rings and flanges, as illustrated.Thus, head assembly 228 rotates within bearings 230,232 while bearings230,232 are allowed limited axial movement within bores 224 and 216. Acounter bore 234 in the left end of head assembly 228 is secured to theend of lead screw 194 by an interference fit so that head assembly 228rotates and translates with lead screw 194. Head assembly 228 alsocomprises at its right end a radially outwardly extending flange 236having a leftwardly facing clutch face 238 positioned to engage theclutch face of insert 214, as shown in FIG. 7. Flange 236 also includesa rightwardly facing clutch face 240 positioned to engage a leftwardlyfacing clutch face 242 provided on the inside surface of a clutch levermounting cap 244 which is threaded into counter bore 210, asillustrated.

Within clutch head assembly 228, a further bore 246 surrounds a clutchspring 248 which bears at one end on the piston end of lead screw 194and is captured at its other end within the central bore of a hollowplunger 250. Surrounding plunger 250 is a threaded plunger adjustmentsleeve 252 which is threaded into the right end of bore 246 and can beadjusted axially to limit the rightward movement of plunger 250.

Within clutch lever mounting cap 244, a central bore 256 slidablyreceives a plunger pin 258 which is movable axially within bore 256under the influence of a clutch actuation lever 260 which is pivoted at262a to the right surface of clutch lever mounting cap 244. In theposition of the apparatus illustrated in FIG. 7, plunger pin 258 ispressed to its maximum into bore 256 so that spring 248 bears on the endof lead screw 194, thereby causing leftwardly facing clutch face 238 tofirmly engage insert 214 and prevent rotation of lead screw 194.

Within counter bore 218 and between bearings 230,232, a constant force,flat spiral spring 262, is positioned, the outer end of spring 262 beingattached to piston 198 and the inner end of spring 262 being attached toclutch head assembly 228. A pair of telescope tubes 264 are welded orotherwise attached to head plate 222 and extend leftward so that theends of cables 46,48 are positioned within the telescope tubes. Meanssuch as plugs 268 are swaged onto the ends of cables 46,48 for slidingmovement relative to telescope tubes 264. Plugs 268 are prevented frompulling out of telescope tubes 264 by means of retaining rings 270.Cables 46,48 pass from cylinder top 176 through means such as ferrules272 which are secured to the armored sheaths of the cables. A coilspring 274 biases piston 198 to the right, brakes-released position. Atits right end, spring 274 is seated within an anti-rotation cup 276slidably mounted within cylinder 200. Cup 276 is attached to head plate222 by means of bolts 278. A pair of axially extending slots 280 areprovided in cup 276 and similar slots 282 are provided in piston 198 inposition to be engaged by anti-rotation screws 284. As a result, thepiston assembly 196 is prevented from rotating in response to torqueapplied by spring 262.

As previously mentioned, FIG. 7 shows the actuator 38 is its releasedposition. In this position, the clutch actuation lever 260 is fullydepressed by the action of the release spring 274 and therefore forcesthe slack adjuster plunger 250 inward against the plunger spring 248,causing the entire plunger spring load to react on lead screw 194 andhold the clutch face 238 in engagement with clutch insert 214. Thus,lead screw 194 will not rotate under the influence of spiral spring 262and whatever clearance exists between the brake shoes 28 and theassociated wheels will be maintained. In this position, if a rail carinspector desires to increase the shoe clearance, he need only pry or"bar back" a brake shoe back so that a rightward force on push rod 178eventually will overcome the preload of plunger spring 248, causingclutch face 238 to move out of engagement with clutch insert 214 andallowing lead screw 194 to rotate in such a direction to wind up spring262. When the car inspector has obtained sufficient clearance andreleases this prying action, the spring 248 will again force clutch face238 against insert 214, preventing spring 262 from unwinding and takingup the slack just introduced. Thus, any amount of clearance required tochange one or more brake shoes is available when the brake is released.0n the other hand, should the car inspector exert excessive force on hispry bar, he will not be able to close the clearance between clutch faces240 and 242 because rightward travel of lead screw 194 will stop againstplunger adjustment sleeve 252 before clutch faces 240,242 can engage.

When air is first admitted to the actuator through port 206, piston 198moves to the left allowing the lever 260 to shift to the position shownin FIG. 8. As long as lever 260 continues to engage the inner surface ofthe brake cylinder, plunger 258 will apply force to spring 248 to urgelead screw 194 and clutch head assembly 228 to the left so that clutchface 238 remains engaged with clutch insert 214 and rotation of lead 194is prevented. However, once movement of piston 198 permits lever 260 tomove outwardly against its stop as illustrated in FIG. 9, spring 248will no longer maintain engagement of the clutch. As a result, thespring 262 will begin to unwind itself and will rotate lead screw 194.Rotation of the lead screw will cause threaded insert 184 and itsassociated push rod 182 to move outward to the left, as illustrated,until contact between the brake shoes 28 and the adjacent wheels isachieved and an engagement force of, say, approximately 50 pounds hasbeen attained. Since spring 262 drives the brake shoes through theirclearance, the air consumption of the actuator is reduced. Furtheradmission of air into the brake cylinder will force the piston furtherto the left. As the force exerted by the piston can only be transmittedto lead screw 194 through clutch faces 240,242, these clutch faces willengage, rotation of the lead screw 194 will be prevented and the forceresulting from air pressure acting on piston 198 will be transmitted tothe brake shoes, causing a brake application proportional to the brakecylinder pressure. The configuration of the apparatus at this stage isshown in FIG. 9. In a typical application, engagement of clutch faces240,242 occurs after approximately 2 inches of actuator travel.

When air pressure is released from the actuator, spring 274 moves piston198 to tne right, bringing lever 260 into contact with the cylinder headonce again. At this point, the trigger is slightly depressed and urgesclutch faces 240,242 apart to the position shown in FIG. 8. After alittle more return stroke, clutch face 238 and insert 214 again engage.Note that when both the right and left clutch faces are separated, anyclearance which might have resulted as a result of shoe wear can betaken up by the unwinding action of spring 262. Once piston 198 hastraveled in the release direction to the position shown in FIG. 8,however, the left clutch faces will be engaged by spring 248 and thedesired brake shoe clearance of, say, 2 inches will be assured.

If a new shoe is installed after the brakes have been released and thetotal brake shoe clearance is less than the desired amount of, say, 2inches, the initial application of the brakes would result in theactuator plunger 250 stopping against its adjustment sleeve 252 before 2inches of travel have occurred. Air pressure acting on the piston 198would force it to the left against the now immovable push rod 182. As aresult, force transmitted through lead screw 194 would cause clutch face238 to move away from insert 214 and thereby permitting lead screw 194to rotate and wind up the spring 262 until the desired amount of pistontravel has been achieved. At this point, the clutch faces 240,242 wouldengage and prevent further let out of the lead screw.

It should be noted that if power spring 262 breaks, the slack adjusteroperates as previously described except that it does not have the fasttakeup feature. When air is admitted to the actuator port 206, thepiston 198 moves and lever 260 pivots to disengage clutch face 238 andclutch insert 214. Since spring 262 is broken the rotation takes placeonly by the continued leftward movement of piston 198. Lead screwrotates in threaded insert 184 to move push rod 182 outward to the left.As the break shoe 28 engages the wheel and has a force of approximately50 pounds, the force of spring 248 is overcome and clutch faces 240 and242 engage preventing further rotation of the lead screw. Since the fasttakeup did not occur, more than one braking cycle is needed to reach thedesired brake shoe clearance.

When the air pressure is released and spring 274 returns the piston tothe right, normal friction will prevent the beam from releasingimmediately. Thus the initial movement of the piston relative to thepush rod 182 causes disengagement of clutch faces 240 and 242 allowinglead screw 194 to rotate further adjusting the spacing. Once the beambegins to move, clutch face 238 and insert 214 engage preventing furtherrotation of lead screw 194.

Having described my invention in sufficient detail to enable thoseskilled in the art to make and use it, I claim and desire to secureLetters patent for:
 1. In a brake rigging for a rail vehicle having atleast one transverse axle; at least one brake beam extended in spaced,parallel relation to the axle and supported by the vehicle for movementlongitudinally of the vehicle; a first pair of brake show carryingheads, one of said first pair mounted on each end of said brake beam,each of said first pair of brake shoe carrying heads comprising pivotmeans formed therewith; a pair of bell-crank levers each having afulcrum and a pair of arms, one of said levers being mounted forrotation in each of said pivot means; and a fluid pressure operablebrake actuator pivotably mounted at one end to one arm of one of saidbell-crank levers and at the other end to one arm of the other of saidbell-crank levers, the improvement comprising;a pair of push rods eachcomprising at one end a clevis having a first axis of rotation, saidclevis having arms with first bores spaced along said axis, a bearingmember positioned between said arms, said bearing member having aconcave spherical bearing surface with a center of curvature positionedon said axis, and means for retaining said bearing member between saidclevis arms; the other arm of each of said bell-crank levers having aconvex spherical bearing surface and a second bore having a second axisextending through the center of curvature of said convex bearingsurface; bearing means extending into said second bore; and meansextending through said first bore and said bearing means for pivotablycoupling said push rods to said bell-crank levers with said sphericalbearing surfaces in contact.
 2. In a brake rigging according to claim 1,wherein the other end of each of said push rods is fixed relative tosaid transverse axle.
 3. A brake rigging for a rail vehicle having atleast one transverse axle; at least one brake beam extended in spacedparallel relation to the axle and supported by the vehicle for movementlongitudinally of the vehicle; a first pair of brake shoe carryingheads, one of said first pair mounted on each end of said brake beam,each of said first pair of brake shoe carrying heads comprising pivotmeans formed therewith; and a pair of bell-crank levers each having afulcrum and a pair of arms, one of said levers being mounted forrotation in each of said pivot means; the improvement comprising:(a) afluid pressure operable brake actuator pivotably mounted at one end toone arm of one said bell-crank levers and at the other end to one arm ofthe other of said bell-crank levers; (b) a pair of push rods eachcomprising at one end a clevis having a first axis of rotation, saidclevis having arms with first bores spaced along said axis, a bearingmember positioned between said clevis arms, said bearing member having aconcave spherical bearing surface with a center of curvature positionedon said axis, and means for retaining said bearing member between saidclevis arms; (c) the other arm of each of said bell-crank levers havinga convex spherical bearing surface and a second bore having a secondaxis extending through the center of curvature of said convex bearingsurface; (d) bearing means extending into said second bore; and (e)means extending through said first bore and said bearing means forpivotably coupling said push rods to said bell-crank levers with saidspherical bearing surfaces in contact.
 4. A brake rigging according toclaim 3 wherein the fluid operable brake actuator comprises:(a) ahousing containing a fluid operating piston; (b) one end of the housingbeing pivotally connected to said one end of one arm of one of thebell-crank levers; and, (c) an actuating push rod connecting the pistonto said other end of one arm of the other of the bell-crank levers.
 5. Abrake rigging according to claim 4 wherein the actuating push rodcomprises a slack adjuster for adjusting the normal spacing of arms ofthe respective said one and said other bell-crank levers.
 6. A brakerigging according to claim 5 wherein the slack adjuster includes anadjusting rod threaded through a nub secured to the actuating push rodand connected at one end through a friction clutch to the piston.
 7. Abrake rigging according to claim 6 wherein the slack adjuster comprisesa torsional spring disposed at said one end of the actuating push rod,the torsional spring having one of its ends secured to the housing andthe other of its ends secured to the adjusting rod for rotating andbeing rotated by the adjusting rod when the clutch is free to rotaterelative to the piston.
 8. A brake rigging according to claim 7 whereincables are attached to the piston to facilitate manual application ofbrakes of the rigging.